Corrosion mitigation for gearbox

ABSTRACT

A magnesium component of a rotary wing aircraft is provided including a groove including a first sidewall and a second sidewall arranged on opposing sides of a recessed opening. The first sidewall includes a deposit positioned adjacent the recessed opening. The deposit is formed by cold spraying one or more layers or powdered material within an area of the first sidewall from which material was removed.

BACKGROUND OF THE INVENTION

Exemplary embodiments of the invention relate to components of a rotary-wing aircraft susceptible to corrosion damage and, more particularly, to a method for preventing or reducing corrosion damage to such a component of a rotary-wing aircraft.

A rotary-wing aircraft includes components, such as gearboxes for example, typically constructed from aluminum and magnesium alloys. As a result of exposure of such components to the environment, these alloy materials are susceptible to corrosion. For example, the presence of water or moisture on the outer surface of the component may cause corrosion and other environmental conditions, such as chemical fallout and saltwater for example, may exacerbate corrosion. Corrosion causes the material of the component to deteriorate, thereby reducing the wall thickness thereof. In some instances, the component's wall thickness may be excessively reduced such that the structural integrity of the component is compromised.

Conventional rotary-wing aircraft component repair methods allow for dimensional restoration of aluminum and magnesium structures using a variety of techniques including, but not limited to, epoxy bonding, plasma spray, high velocity oxygen fuel (HVOF) thermal spray and fusion welding for example. High temperature repair techniques may result in unacceptable component distortion and degrade the substrate material properties by over-aging or solutioning. Epoxy bonding can break or spall during service, allowing the environmental elements to attack the underlying material. Subsequent attacks on the material will deteriorate wall thickness such that the component is no longer usable.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment of the invention, a magnesium component of a rotary wing aircraft is provided including a groove including a first sidewall and a second sidewall arranged on opposing sides of a recessed opening. The first sidewall includes a deposit positioned adjacent the recessed opening. The deposit is formed by cold spraying one or more layers of powdered material within an area of the first sidewall from which material was removed.

According to another embodiment of the invention, a method of rebuilding a damaged portion of a groove in a magnesium component is provided including forming an area in a sidewall adjacent the recessed opening by removing all material exhibiting wear or localized corrosion and pitting. A deposit is created in the area and is integrally formed with the sidewall and an inner surface of a recessed opening of the groove. Excess material is removed as needed, from the deposit.

According to another embodiment of the invention, a method of preemptively forming a deposit in a groove of a magnesium component is provided including removing material from a sidewall adjacent a recessed opening of the groove to form an area. Damage is expected to occur in the area from which the material is to be removed. A deposit is formed in the area. The deposit is integrally formed with the sidewall and an inner surface of the recessed opening. Excess material is removed as needed, from the deposit.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of an exemplary rotary wing aircraft;

FIGS. 2a and 2b are exemplary schematic diagrams of the main rotor system and the tail rotor system of the aircraft of FIG. 1;

FIG. 3 is a perspective view of a gearbox housing of a rotary wing aircraft according to an embodiment of the invention;

FIG. 4 is a cross-sectional view of a portion of the gearbox housing illustrated in FIG. 3 including a groove;

FIG. 5 is a cross-sectional view of a portion of a gearbox housing having an integrally formed deposit according to an embodiment of the invention;

FIG. 6 is a method for rebuilding a portion of a groove of a gearbox housing according to an embodiment of the invention; and

FIG. 7 is a method for preemptively forming a deposit in a groove of a gearbox housing according to an embodiment of the invention.

The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a main rotor system 12. The aircraft 10 includes an airframe 14 having an extending tail 16 which mounts a tail rotor system 18, such as an anti-torque system, a translational thrust system, a pusher propeller, or a rotor propulsion system for example. Power is transferred from one or more engines E to a power transmission gearbox 20 (see FIGS. 2a and 2b ), to drive the main rotor system 12 about a respective axis of rotation A. Although a particular rotary wing aircraft configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as a high speed compound rotary wing aircraft with supplemental translational thrust systems, a dual contra-rotating, coaxial rotor system aircraft, and a turbo-prop, tilt-rotor or tilt-wing aircraft for example, will also benefit from the present invention.

Referring now to FIG. 2a , a schematic diagram of the main rotor system 12 and the tail rotor system 18 of the aircraft 10 of FIG. 1 is provided in more detail. In the illustrated non-limiting embodiment, the power transmission gearbox 20 is interposed between one or more engines E, the main rotor system 12 and the tail rotor system 18. The gearbox 20 may be mechanically connected to and configured to operate both the main rotor system 12 and the tail rotor system 18. In another embodiment, shown in FIG. 2b , the rotary wing aircraft 10 includes a first power transmission gearbox 20 a mechanically coupled to and configured to operate the main rotor system 12. Similarly, a second power transmission gearbox 20 b is mechanically connected to and configured to operate the tail rotor system 18. Each of the power transmission gearboxes 20 a, 20 b receives power from at least one engine E of the aircraft 10.

Each power transmission gearbox 20 is generally mounted within a housing 22 (see FIG. 3) configured to support the gear-train therein. In one embodiment, the gearbox housing 22 includes a magnesium material. In the illustrated, non-limiting embodiment, the housing 22 generally includes a plurality of first openings 24 and a plurality of second openings 26. The plurality of first openings 24 may be configured to provide a plurality of passageways for a lubricant to various portions of the gearbox 20 for example. The plurality of second openings 26 may be configured to at least partially support an input module attachment (not shown), such as the rotor shaft (not shown) of the main rotor system 12 or the tail rotor system 18 for example. Although a particular gearbox housing 22 configuration is illustrated and described in the disclosed non-limiting embodiment, other configurations are within the scope of the invention.

The gearbox housing 22 additionally includes one or more grooves 30, as illustrated in FIG. 4, having a recessed opening 32 surrounded on opposing sides by a similar first and second sidewall 34. Each groove 30 is configured to receive a component, such as an o-ring seal for example. In one embodiment, the plurality of grooves 30 are arranged within one or more of the plurality of first openings 24 or the plurality of second openings 26, as illustrated in FIG. 4, such that the sidewalls 34 are formed by the housing 22. However, the grooves 30 may be formed in any portion of the gearbox housing 22.

Portions of the housing 22, in particular the sidewalk 34 of the grooves 30 are highly susceptible to wear, as well as to corrosion and/or pitting. Referring now to FIG. 5, a deposit 40, illustrated as a shaded region, forms at least a portion of one or more of the sidewalls 34 of a groove 30 in the gearbox housing 22. The deposit 40 may be formed from any suitable powdered material known in the art, such as aluminum or aluminum alloy for example. In one embodiment, the deposit 40 is formed as a means of repairing the housing 22 after wear or corrosion and pitting has already occurred. In another embodiment, the deposit 40 is formed as a “preemptive repair” based on a determination of where damage to the sidewall 34 is most likely to occur.

Each deposit 40 is formed by applying one or more layers of powdered material to an area 42 of the sidewall 34 adjacent the recessed opening 32. In embodiments where the deposit 40 is applied to the housing 22 after damage has occurred, the area 42 is formed by removing the damaged material from the sidewall 34. In one embodiment, the material removed to form area 42 extends from the inner surface 38 of the recessed opening 32 to the outer surface 36 of the sidewall 34 and has a depth sufficient to completely eliminate all of the localized damage or corrosion. Some of the adjacent non-compromised material of the sidewall 34 may additionally be removed along with the damaged material to ensure that the remaining material of the sidewall 34 has not been compromised. In embodiments where the deposit 40 is applied “preemptively,” each area 42 is created by removing material from the sidewall 34 where damage and/or corrosion and pitting are most likely to occur.

The layers of powdered material used to form the deposit 40 are generally applied through a deposition process that provides sufficient energy to accelerate the particles to a high enough velocity such that the particles plastically deform and bond to the area 42 upon impact. The particles of the powered material are accelerated through a converging/diverging nozzle 52 of a spray gun 50 to supersonic velocities using a pressurized or compressed gas, such as helium, nitrogen, other inert gases, or mixtures thereof. The deposition process does not metallurgically transform the particles from their solid state. Various techniques may be used to achieve this type of particle deposition, including but not limited to, cold spray deposition, kinetic metallization, electromagnetic particle acceleration, modified high velocity air fuel spraying, or high velocity impact fusion (HVIF) for example.

The layers of powered material may be applied to the original material of the housing 22, or alternatively, may be applied to a previously formed deposit 40. During deposition of the powdered material, the gearbox housing 22 may be held stationary or may be articulated or translated by any suitable means (not shown) known in the art. Alternatively, the nozzle 52 of the spray gun 50 may be held stationary or may be articulated or translated. In some instances, both the gearbox housing 22 and the nozzle 52 may be manipulated, either sequentially or simultaneously.

A method 100 for rebuilding a damaged portion of a groove 30 of a gearbox housing 22 is illustrated in FIG. 6. The method begins in block 102 by removing all of the localized damage from at least one of the sidewalls 34 of the groove 30 to form an area 42 (see FIG. 5). The corrosion and pitting may be removed either mechanically or chemically, for example using grinding, machining, etching, or other applicable techniques. In block 104, at least one layer of powdered material is applied to the area 42 using a cold spray deposition process to create a deposit 40 integrally formed with the inner surface 38 of the recessed opening 32 and the remainder of the sidewall 34. When bonded to the area 42, the deposit 40 may extend beyond the original dimensions of the sidewall 34 of the gearbox housing 22. After formation of the deposit 40, excess material is removed as necessary, as shown in block 106. As a result, the deposit 40 is generally flush with the remainder of the sidewall 34 of the gearbox housing 22 and/or the dimension of the gearbox housing 22 including the deposit 40 is substantially equal to the original dimension thereof.

A method 200 of preemptively forming a deposit 40 in a sidewall of a housing 22 is illustrated in FIG. 7. The method 200 begins in block 202 by removing some material from the sidewall 34 of an unused gearbox housing 22, at a position where localized corrosion and pitting is most likely to occur, to form an area 42. Material may be removed from the sidewall 34 either mechanically or chemically, for example using grinding, machining, etching, or other applicable techniques. In block 204, at least one layer of powdered material is applied using a cold spray deposition process to form a deposit 40. The deposit 40 formed within the area 42 of the sidewall 34 may extend beyond the original dimension of the surface 30 of the gearbox housing 22. In such instances, excess material is removed after formation of the deposit 40, as shown in block 206. The excess material 40 may be removed so that the deposit 40 is substantially flush with the remainder of the sidewall 34 of the gearbox housing 22 and/or so that the dimension of the gearbox housing 22 including the deposit 40 is generally equal to the original dimension thereof.

Formation of one or more deposits 40 in the sidewalls 34 of one or more grooves 30 in a gearbox housing 22 can reduce and/or prevent corrosion and pitting, thereby improving the life of the housing 22. In addition, use of a cold spray deposition process will not affect the heat treatment condition of the magnesium substrate and its material properties, a consideration which normally limits the availability of repairs of magnesium components.

While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims. 

What is claimed is:
 1. A method of rebuilding a damaged portion of a groove in a magnesium component, comprising: forming an area in a sidewall by removing all material exhibiting wear or localized corrosion and pitting, the sidewall defining a portion of a recessed opening located within a central portion of the groove; creating a deposit in the area, the deposit being integrally formed with the sidewall and an inner surface of a recessed opening of the groove; and removing any excess material from the deposit.
 2. The method according to claim 1, wherein the magnesium component is a gearbox housing of a rotary wing aircraft.
 3. The method according to claim 1, wherein the deposit includes one or more layers of powdered material applied to the area through a cold spray deposition process.
 4. The method according to claim 3, wherein the powdered material includes aluminum.
 5. The method according to claim 1, wherein the deposit extends from an inner surface of the recessed opening to an outer surface of the sidewall and has a depth configured to completely eliminate all damage from the sidewall.
 6. The method according to claim 1, wherein excess material is removed so that the deposit is substantially flush with an outer surface of sidewall.
 7. The method according to claim 1, wherein excess material is removed so at least one dimension of the magnesium component including the deposit is substantially equal to an original dimension thereof.
 8. A method of preemptively forming a deposit in a groove of a magnesium component housing, comprising the steps of: removing material from a sidewall to form an area, wherein damage is expected to occur in the removed material, the sidewall defining a portion of a recessed opening located within a central portion of the groove; forming a deposit in the area, the deposit being integrally formed with the sidewall of the magnesium component and an inner surface of the recessed opening; and removing any excess material from the deposit.
 9. The method according to claim 8, wherein the magnesium component is a gearbox housing of a rotary wing aircraft.
 10. The method according to claim 8, wherein the deposit includes one or more layers of powdered material applied to the area through a cold spray deposition process.
 11. The method according to claim 10, wherein the powdered material includes aluminum.
 12. The method according to claim 8, wherein excess material is removed so that at least one dimension of the magnesium component including the deposit is substantially equal to an original dimension thereof. 